Washing machine appliances generally include a cabinet which receives a tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly is coupled to the wash tub and configured to rotate the wash basket within the wash tub in order to cleanse articles within the wash basket. Upon completion of a wash cycle, a pump assembly can be used to rinse and drain soiled water to a draining system.
Washing machine appliances include vertical axis washing machine appliances and horizontal axis washing machine appliances, where “vertical axis” and “horizontal axis” refer to the axis of rotation of the wash basket within the wash tub. Vertical axis washing machine appliances typically have the wash tub suspended in the cabinet with damping devices. Vertical axis washing machine appliances exhibit vibration harmonics and work in a wide range of rotational speeds. Vibration has been addressed through use of fixed friction damping devices, tuned to one condition that requires the greatest amount of friction.
However, fixed friction type damping devices may have a number of undesirable issues. For example, the damping forces provided by a fixed friction type damping device may be non-uniform. Specifically, the damping forces may vary with movement speed, temperature, or the age of the damping device. If friction increases temperature to certain levels, a piston within the damping device may be damaged or welded onto a wall of a surrounding casing. The close tolerances and interference fit demanded by friction type damping devices may also create difficulties during assembly. Furthermore, the materials that may suitable for such applications are substantially limited. Further still, once assembled, fixed friction type damping devices may poorly accommodate the wide range of mass, imbalance, and rotational speed seen in vertical axis washing machine appliances.
Accordingly, a need exists for a damping device with features for addressing one or more of the above-identified issues. In particular, a damping device for a washing machine appliance that includes features for restricting damping motion without relying upon damping friction would be advantageous.